The proposed research project involves the application of our new method for the measurement of oxygen concentration profiles in living animal tissues and cells. This technique is based on the observation that the fluorescence emission of pyrenebutyric acid is quantitatively quenched by oxygen. Thus, by monitoring either the fluorescence intensities or lifetimes of pyrenebutyric acid which is administered to biological samples by injection, topical application or in microcapsules, the local concentration of oxygen can be determined. Both the spatial and temporal variations of oxygen concentration can be monitored permitting the resolution of the questions regarding the transport and utilization sites for oxygen in living systems. The specific objectives of this project include: (1) the upgrading of the data handling system to increase our ability to analyze the large number of data points, which are produced by our television system; (2) the determination of oxygen concentration profiles within tissue slices and cells in order to determine the mechanism of tissue oxygen transport; (3) the determination of oxygen concentration distribution of the surfaces of skin and exposed organs in living animals and (4) the determination of the effect on oxygen concentration profiles of agents which are believed to facilitate or inhibit tissue oxygen transport.